1. Field of the Invention
The invention disclosed herein relates to a handheld spectrometer that exhibits beneficial aspects of MEMS based Hadamard spectrometers while improving the wavelength resolution and extending the wavelength range beyond one octave.
2. Description of the Related Art
Current diffractive MEMS based Hadamard spectrometers have advantages over traditional scanning grating spectrometers. One example is provided in U.S. Pat. No. 7,791,027, entitled “Apparatus and Method Providing a Hand-Held Spectrometer.” This patent discloses an IR spectrometer that includes a light source adapted to illuminate a sample, a grating adapted to spectrally disperse a light that has illuminated the sample, a MEMS array adapted to be electrostatically actuated by a controller to control a diffraction of the light, a detector configured to detect the light, and a power source adapted to supply power to the light source and to the MEMS array, wherein the controller is adapted to control the MEMS array so as to manage a power consumption of the IR spectrometer. In one embodiment, the IR spectrometer includes a housing sized and arranged to house the light source, the grating, the MEMS array, the controller, the detector, to and the power source in a hand-held device.
Spectrometers of this kind exhibit improved signal-to-noise benefit from using the Hadamard technique, use of a single element detector, and excellent shock-resistance. However, these spectrometers have limited resolution and wavelength range, making it desirable to have different models when the wavelength range or resolution requirements change. Generally, wavelength resolution is based on the capability of the MEMS chip. The wavelength range is limited by the use of a single order diffraction grating to one octave, meaning that the ratio of the longest wavelength to the shortest wavelength is less than or equal to two.
Thus, what are needed are methods and apparatus to provide a handheld spectrometer that exhibits the beneficial aspects of MEMS based Hadamard spectrometers while improving the wavelength resolution and extending the wavelength range beyond one octave.